The subject matter disclosed herein relates to a remote detonator system for explosive charges and in particular to a remote detonator system having wireless communications between a transmitter and a detonator.
Explosive charges are used in a wide variety of applications, such as mining operators, building demolition and in military and police operations. The initiation of the explosive charge is performed by a detonator device that typically uses an electrical charge to ignite a small explosive such as a blasting cap for example. Traditionally, the blasting cap was physically connected to an ignition switch using a conductor such as copper cable. To initiate the detonator, the operator connects the conductor to the switch once the area where the explosive charge is clear of personnel and actuates the switch. The use of a physical conductor provides a number of advantages in reliability and safety.
However, physical conductors also introduce a number of issues. In applications such as mining, many explosive charges may be set and configured to detonate in a desired sequence. The use of physical conductors to connect with each of the charges is labor intensive and dependent on the accuracy and attention of the operator to ensure the large number of conductors are properly installed and coupled to the switch. A misconnected conductor increases the risk of detonating the explosives in the wrong sequence. In other applications, such as military operations, the use of a physical wire is undesirable as it increases the weight of equipment the personnel have to carry and may expose the personnel to opposing forces while the conductor is being disbursed and is subject to damage prior to actuation of the detonator. Further, physical wires are susceptible to induced currents due to radio frequency electromagnetic fields created by radios and other wireless communications devices. This induced current may in certain circumstances cause a premature detonation of the explosive charge.
Other types of physical connections have also been proposed, such as but not limited to shock tubes, optical cables, low energy detonating cord (LEDC) and the like. While each of these has its own advantages, since the connections are physical, care must still be taken by the operator during installation. Further, physical connections may also become a tripping hazard for friendly forces or provide a means for an opposing force to locate either the explosive charge or personnel.
To avoid these issues, wireless detonator systems have been proposed. The use of a wireless system solves the labor issue of the having to install a conductor and also reduces the installation time for military personnel. However wireless detonator systems have provided their own challenges. First, since there is no physical conductor, the detonator needs to include an energy source to initiate the detonator. This presents a risk of inadvertent detonator actuation. Further, many of these systems use radio frequency (RF) communications. An RF based communications system uses an antenna to acquire the signal. This can be problematic in some applications, such as a battlefield where the RF spectrum is heavily used. Since RF signals are an electromagnetic wave, stray (and directed) RF signals may induce an electrical current in the antenna, which presents a risk of inadvertent detonator actuation. Further, RF communication is susceptible to electromagnetic jamming by both friendly and opposing forces, which could prevent initiation of an explosive charge.
Other wireless systems, such as optical or laser systems have also been proposed. These resolve the issue of interference, induced voltage and jamming. However an optical based system requires a line of sight connection with no obstacles for communicating the signal from the switch to the detonator. This situation may not be possible in some applications, such as urban warfare where the operator may be several rooms away from the explosive charge. Further, a line of sight system may expose the operators to opposing forces or otherwise reveal their position.
Accordingly, while existing detonator systems are suitable for their intended purposes the need for improvement remains particularly in providing a wireless communication system between a detonation transmitter and a detonator that does not utilize radio frequency communications.